This invention relates to an apparatus and a method for preventing tooth decay using electromagnetic radiation.
Tooth decay is caused by demineralization of the tooth structure at either the enamel or root surface. The enamel is a thin layer (1-2 mm) composed of a crystal-type structure of hydroxyapatite or calcium phosphate hydroxide, containing large amounts of calcium and phosphorus. Dental enamel is a porous material and although it contains about 96% by weight of mineral, this is equivalent to approximately 85 percent by volume. The remaining 15 percent by volume is made up of water, protein and lipid, which form the diffusion channels through which acids and minerals can travel into or out of the tooth. The dentin, the major part of the core of the tooth, is composed of CaCO3, a chalk-like material. Although it is 70% by weight of mineral, it also contains 20% by weight organic and 10% by weight water. This corresponds to 47% by volume mineral.
Tooth decay, or dental caries results from the growth of bacteria on the tooth. The bacteria metabolize sugars to acid which can dissolve the tooth. The bacteria grow as a plaque on the tooth and conventional treatment involves periodic removal of the plaque and strengthening of the tooth to make it more resistant to the acid produced by the bacteria.
The majority of tooth decay occurs in the occlusal and unexposed surfaces of the tooth. The tooth is composed of the lingual (back), buccal (front), and occlusal (top) surfaces. The lingual and buccal surfaces are considered to be xe2x80x9cflatxe2x80x9d although there are grooves and fissures. The occlusal surface is very uneven, composed of pits, fissures, and protuberances. Because of the way the teeth are formed in the mouth, there are also unexposed surfaces of the tooth, such as subgingival surfaces, interproximal surfaces, and contact surfaces.
Methods to prevent tooth decay have typically concentrated on the buccal and lingual surfaces. Unexposed surfaces are usually not treated. Sealants are consistently used on the occlusal surfaces because other methods are relatively ineffective on the occlusal surfaces due to the very different structure and composition of the occlusal surface. The differences include a harder and more fissured surface, the enamel is generally thicker and the structure possesses a different angulation of prisms. In addition, fluoride has previously been shown to be ineffective on the occlusal surface.
Common professional methods to prevent tooth decay have included fluoride, pit and fissure sealants, and varnishes. However, none of these methods individually protect all of the tooth surfaces nor are they permanent, usually lasting less than 5 years. In addition, heat treatment has been explored as an alternative method. By treating the tooth with a very high heat, from 250-1000xc2x0 C., the structure of the tooth is changed, making it more resistant to acid. This method has never been used clinically because of safety concerns. Because most of the changes to the tooth occur at a very high heat, 1200xc2x0 C., some changes occur between 500xc2x0 C. and 1000xc2x0 C. and a few were seen at temperatures as low as 250xc2x0 C. to 400xc2x0 C., there is the potential for thermal damage to the underlying pulpal tissue, adjacent soft tissue and osseous structures. Therefore, although the effects of laser irradiation on dental caries and tooth structure were explored some 30 years ago, the risk of thermal damage to the adjacent hard tissue and pulp was such that much of the research was abandoned. Several laser wavelengths have been explored, including CO2 and Nd:YAG, but both produce a significant amount of heat on the surface of the tooth and in the pulp and provide only a shallow treatment of the tooth itself. With improved laser technology, a number of different types of lasers with varying tissue penetration and energy levels have been developed.
The structural changes produced during the application of heat by CO2 and Nd:YAG lasers at these very high heats include a change in the phosphate molecule in the hydroxyapatite. This makes the tooth less soluble and increases resistance to decay. However, the level of heat produced by these lasers has not been used clinically because it has been shown to damage the tooth structure itself as well as potentially damaging soft tissue.
The action of the laser, as well as other types of tooth treatments, to produce resistance of the tooth to acid can be envisioned as follows: it has been hypothesized that tooth enamel crystals (xe2x80x9chydroxyapatitexe2x80x9d) possess two types of sites from which dissolution can occur. The first type of site (the xe2x80x9cthermalxe2x80x9d site) is less resistant to dissolution by acids under conditions typically found in the oral environment than is the second type of site (the xe2x80x9cchemicalxe2x80x9d site). The treatment of tooth enamel by carbon dioxide laser irradiation or by high temperatures eliminates or reduces the thermal sites, leaving only the chemical sites for dissolution to occur. Once the thermal sites have been eliminated, the tooth enamel is then treated to eliminate the chemical sites with dissolution rate inhibitors or chemical agents. However, even if such laser treatments were clinically usable for safety reasons, they have the disadvantage that they produce only a surface treatment and cannot protect all of the tooth structure, particularly the occlusal and unexposed surfaces.
Therefore, all of these methods are rendered undesirable by that fact that they can only provide temporary treatment, act only at a very shallow depth of the tooth at the lingual and buccal surfaces, and some cannot be used due to safety issues. In addition, none of the above methods can be used in a non-professional setting.
One aspect of the invention is a method of treating a living tooth in a mammal""s mouth, comprising irradiating the unexposed and occlusal surfaces of said tooth with light having a wavelength in the range of between from about 400 nm to about 810 nm, and an energy and an energy density sufficient to vaporize water and organic material without damaging the pulp of the tooth. In one embodiment, the treatment heats the localized sites to a temperature of no more than about 250xc2x0 C. In a further embodiment, the treatment heats the localized sites to a temperature of no more than about 200xc2x0 C. In a further embodiment, the treatment heats the localized sites to a temperature of no more than about 100xc2x0 C. In a further embodiment, the treatment heats the localized sites to a temperature of no more than about 50xc2x0 C. In one embodiment, the unexposed surfaces are the subgingival, interproximal, and contact areas of the tooth.
Preferably, the vaporization of organic material and water occurs from 3 microns to 50 microns beneath the surface of the tooth. The energy density may be between about 5 J/cm2 to 65 J/cm2, preferably about 5 J/cm2 to 30 J/cm2, and more preferably between about 5 J/cm2 to 12 J/cm2.
In one embodiment, the method further includes bonding a chemical agent to the crystalline structures of the tooth after removal of the organic compound.
In one embodiment, the light beam is a coherent light source, such as a laser, preferably an argon laser or a diode laser. In one embodiment, the argon laser beam is applied at 250 mW. In a further embodiment, the light beam is an incoherent light source, preferably an LED.
In one embodiment, the chemical agent is fluoride, including an effective concentration of fluoride is less than or equal to 200 ppm of stannous fluoride (0.08%) or 1000 ppm of sodium fluoride (0.275%). Typically the fluoride acts by binding to hydroxide groups within the hydroxyapatite crystal.
In one embodiment, the laser is applied for 10 seconds for each treated surface. Alternatively the tooth is treated for a period of time of more than 1 sec for each treated surface.
A further aspect of the invention is an apparatus for the treatment of a tooth, comprising a handpiece and a light source having a wavelength in the range of between from about 400 nm to about 810 nm. In one embodiment, the light is output transverse to the longitudinal axis of the handpiece. The handpiece is adapted to provide at least two spot sizes for the output beam. Preferably, this is accomplished by providing interchangeable tips, one of which provides a relatively large spot size for treating lingual and buccal surfaces, and the other of which provides a relatively small spot size for treating at least interproximal surfaces.
In one embodiment, a method of treating between teeth is disclosed, which includes irradiating said tooth surface with a laser. In a further embodiment, the method further comprises applying fluoride to a tooth surface, including the occlusal and unexposed surfaces prior to or after irradiation.